1. Field of the Invention
The present invention relates generally to snow-making equipment. More particularly, this invention relates to a nucleator for generating ice crystals for seeding water droplets in snow-making systems.
2. Description of Related Art
The production of artificial snow is well-known in the art. Currently there are generally four different methods of snow-making: (1) fan guns, (2) internal mix air and water guns, (3) external mix air water guns and (4) water only guns.
Fan guns consist of a large barrel with an enclosed electric fan that forces large volumes of ambient air through the barrel. On the end of the barrel there is a configuration of water nozzles usually arranged in banks that can be turned on independently of each other. Each bank can consist of up to 90 small capacity hollow cone nozzles which produce very fine particles. The water particles are projected into the ambient air by the large volume of air that the fan produces. Fan guns may include an outer ring that is called the nucleating ring. This ring has a small number of miniature air/water nozzles that operate in the same way as an internal mix air/water gun. An onboard compressor is used to operate this ring. The nucleating ring's primary role is to produce ice crystals. The ice crystals are carried along the outside of the bulk water plume for a distance before becoming ingested into the plume thus nucleating the bulk water plume. Operation of the fan gun is achieved by opening one bank of nozzles at a time and altering the water pressure to the nozzles. Once full pressure is achieved on a bank another bank is opened and the water pressure is adjusted.
Internal mix air and water guns consist of a compressed air line and a water line converging into a common chamber with an exit orifice. Compressed air enters the common chamber and expands breaking up the water stream into smaller particles and projecting them into the ambient air. Operation of the gun is achieved by regulating the water pressure entering the common chamber. A common feature of the internal mix gun is that when water flow is increased air flow is decreased and vice versa. Water pressure cannot usually exceed the air pressure which is usually 80-125 psi. There are a multitude of orifice and mixing chamber shapes that produce a wide variety of plumes and droplet sizes.
External mix air and water guns usually consist of a configuration of fixed orifice flat jet nozzles arranged on a head that spray water into the ambient air. The head is usually put on a mast in order to give the water droplets more hang time due to the fact there is no compressed air to break the water droplets into smaller particles or to propel them. As with the fan guns the external mix guns may include nucleating nozzles that use small internal mix nozzles to produce ice crystals which are directed into the bulk water plume. Control of the gun may be achieved by changing the fixed orifice flat jet nozzles for a different size or opening banks of nozzles as with the fan gun.
Water only snow guns have no compressed air or nucleating nozzles. The head of a water only snow gun comprises a number of flat jet nozzles assembled on a high mast, usually a minimum of 6 m in height. Snow guns of this type can only be used at temperatures starting at −6° C. and work better with a high temperature nucleation additive.
These various types of snow guns or snow lances are employed with particular application in winter sports recreation areas. Generally, the most effective way to generate artificial snow is to nucleate water droplets projected into cold air. The stream of tiny water droplets is thus mixed in the atmosphere with a stream of nucleating agents, typically tiny ice crystals. The two different streams of water particles are configured to intersect in a region referred to as a germination region where snow may be formed by the combination of the two different streams of water particles. The ice-seeded water droplets form snowflakes as they continue to freeze along their gravity dependent trajectories in the air and eventually fall to the ground to form snow. This artificial snow is particularly useful for supplementing natural snowfall at ski and snowboard resorts.
This application is primarily concerned with the nucleating agents and the mechanisms and techniques for generating them and combining them with streams of water particles. Such nucleating agents may consist of tiny ice particles or nuclei which may be formed using a “nucleator”. A nucleator generally forms the stream of tiny ice particles using compressed air and cold water in a mixing chamber before expelling the tiny ice particles out of an exit orifice or nozzle. U.S. Patent Application Publication No. 2011/0049258 A1 to Lehner et al., incorporated herein by reference for all purposes as if fully set forth in this specification, discloses a conventional nucleator nozzle having an axial compressed air inlet opening at one end that directs compressed air into an axial nozzle channel. This conventional nucleator nozzle also includes a lateral water inlet opening which feeds water into the nozzle channel at an angle perpendicular to the nozzle channel axis. The compressed air and water combine in a mixing chamber portion of the axial nozzle channel. The combined water and air mixture is then directed toward an exit orifice or nozzle.
The exit orifice or nozzle of Lehner et al. is a conventional convergent-divergent nozzle configuration. That is to say that the nozzle channel tapers in diameter in a first section down to a core, or narrowest, diameter. In a second expanding region, the nozzle channel expands from the core diameter to an outlet opening with greater diameter than the core diameter. The expanding region of a convergent-divergent nozzle typically generates a negative pressure which, when combined with the compressed air and water mixture, generates tiny ice particles when ejected into cold air.
While conventional nucleators, including those disclosed in Lehner et al. generate nucleating particles useful for snow-making, improvements to nucleators are needed to increase the efficiency and reduce the cost of operation while offering a more robust snow-making gun that operates in a wide range of ambient conditions. Accordingly, there exists a need in the art for an improved nucleator for generating ice crystals for seeding water droplets in snow-making systems.